You're The Lesson I Never Learned
by Lady Venom2
Summary: Leonardo always knew his Leadership would be tested in unusual ways, but when one young woman tests him in ways he never thought, will he be able to say no, and save the heart of a brother?


**You're The Lesson I Never Learned**

By: Lady Venom

He felt her shift her weight, and pause; body stiffening. Reaching over, he pulled her close, arm wrapping around her waist as her back came to rest against his plastron. Her naked body felt good next to his. He hoped silently, and with some shame, that his brother would work into the early hours again.

He knew it wasn't right. To desire was one thing, but to act upon the lust he felt. Even if it were consensual, he should have had more restraint, but each time his brother would become obsessed with something new, he would hole himself up for weeks on end. Barely sleeping or eating. The woman he had taken as his own began to doubt his love for her, a woman already in constant doubt of her worth.

She sighed and settled against him, he looked past the soft tendrils of hair to the door. Beside it, sat a chair holding all his straps and gear. His katana's, mask and all the responsibilities of leading were there.

She always took his mask off. He had a suspicion it was so she could pretend he was his brother. She would never go to Mikey, those two were as brother and sister. Nor would Raphael allow her to go to him, having promised his brother that he wouldn't touch her. Raphael always kept his word, even if he didn't care to. He had enough honour to respect his brother's wishes.

_And me? I doubt he ever thought he'd have to worry about me._ _Some leader I am._

He was so lost in his thoughts, that it took a moment to realize that she was pulling away. He didn't say anything, just watched her as she pulled on her jeans, her bra and shirt, and finally her socks.

She turned back to him, leaning knee on the edge of the bed as she leaned in close to him, pulling his face in tenderly for a good bye kiss that he accepted. He longed to tell her '_stay here_, _I won't ever ignore you_.' He knew he wouldn't, because he didn't want to hurt his brother anymore that what he had. But to see them together, happy, as if she had never graced his bed, hurt worse than any blade.

He knew that only Raphael knew of the tryst, and besides the occasional warning to stop, he had never really done anything to worry the leader. He surmised it was his compassion for his brother, and not wanting to hurt him. He watched her leave, and rolled back over, getting ready to fall asleep when there was a knock on the door.

Rolling over, he sat up in bed.

"Come in."

The door opened slowly, admitting a small, wizened old rat in a tattered brown robe.

"Master Splinter?" He stood immediately and went to bow before his father.

The rat gave Leonardo a sad look as he watched his prize pupil.

"My son, do you recall the tale of how my Master and Saki came to begin the feud?"

The realization of what his father meant caused an uneasy stirring within him.

"But sensei, I would never hurt Donatello intentionally, she comes to – "

Splinter silenced him with a wave of his claw.

"My son, intentional or not, you are not to allow Cassandra into your bed again. She, no doubt, felt her reasons justified, but it will only cause strife if you continue."

Leo, struggling to find a way to explain away his actions, simply bowed deeply, bidding goodnight to his father and sensei.

Sleep was a long time in coming that night.

* * *

It had been two weeks, two weeks of nights without her. Cassandra and Don had been the happy couple he thought them to be, and Leo wished with childish optimism, that he would never need to tell her no. That the problem would right itself.

"Hey, Leo? You've been staring off into space for a while now, bro!"

Blinking, the eldest turtle looked up at the concerned face of Donatello.

"I was? Wow, sorry Don. Is some the matter?" He asked, eyes glancing behind his brother to Cassandra, who was laughing as she and Mikey played video games.

"Actually yea. There are some new parts I need for my computers, and I just wanted to let you know that I'll be gone, probably till morning."

Leonardo nodded; his insides twisting as thoughts ran through his mind, each one a mish-mash of Cassandra and him.

"Thanks, uh, for the heads up Donny."

Don nodded and turned, going back over to where Cassandra was pressing buttons furiously. The technologically inclined of the four watched, waiting for a break in the game. When one came, he wrapped his arms around her with such open adoration and a quick kiss followed by a soft '_I love you'_. And he was out the door.

Watching Cassandra, Leo could see a visible difference in her demeanour. Her usual happy go lucky smile was gone, and a distant look had crept into her eyes. Her body had literally slumped. It was like her very life had left with his brother's departure.

He wanted to go to her so badly, but, he knew he couldn't. He was at a loss for what to do, when he caught sight of his hot-tempered brother going to the dojo. Following him in, he said not a word. All he wanted was to stave off the excess energy that coursed through him and rid his mind of unwanted thoughts.

"So I noticed Donny's gone fer the night." Raph sneered, blocking the swift, downward slice of the katana.

"Yes, he has. And what has that to do with anything? Besides Cassandra keeping warm alone in Don's bed?" Leo side-stepped a kick and thrusted towards Raphael's mid-section.

"You sure 'bout that Leo? You really think you can say no?" Raphael blocked another attack.

"Yes, I, do!" Came the forced words between the grunts of attacks that Leo was inflicting upon his brother.

Raphael laughed sardonically at the naiveté of his older brother.

"Leo, mark me, if you let 'er… I _will_ make ya regret it."

"Oh really? As leader don't you think the decision is mine to make?" Came the sarcastic, self-absorbed reply.

Raphael drop kicked Leonardo to the floor.

"Yea? Well, you forfeited that role when ya turned yer back on your brother!"

"I don't need this Raph; I've got my own conscious!" Leo jumped to his feet, glaring at the red-banded turtle.

"Just back off, I can take care of things!"

"Yea, sure ya can." Raph said, getting in close, his hot breath washing over Leo. "So good in fact, I had to tell Master Splinter what was goin' on last time."

Leo's eyes went wide with a shocked realization; and he dropped down, leg shooting out to connect with Raph's as he knocked him to the floor.

"You told father? Do you have any idea the looks he gave me since then? I…I disappointed him, so much…"

Still on his back, Raphael kicked out with his foot, hooking it against Leo's to pull him down.

"Yea? Ever think ya deserved that?"

"Argh! Leave me alone!"

Jumping up, Leo stalked from the room, heading for the showers.

Getting to his feet, Raph glared at his brothers retreating form. "You're the one who followed me…" He muttered, wiping sweat from his brow.

* * *

Mikey glanced up from his card game with Cassandra to watch Leo stalk by.

"Hey, Leo, wanna play crazy eights? Cassy's really good!"

To prove the point, the red-haired woman laid down her last card and grinned triumphantly at Michelangelo, but her eyes slid to Leo's, and he suddenly wondered if it were just the card game she was happy at winning.

"No thanks, maybe another time. I have to go meditate."

The smile faltered on Cassandra's lips. She gave a soft sigh and turned back, listening to Mikey's incessant chatter.

Up in his room, he sat on a mat on the floor, crossing his legs and, resting his shelled back against the wall, began to clear his mind. It was hard, as excuses began to float to the surface, how to tell Cassandra no, how to be strong when her delicate fingers begin to trail along his arm. Her green eyes will look so lost, that the guardian in him will bang against his will to get through in order to comfort her.

But he won't ever make the first move. His whole body will tremble with desire to touch her, kiss her. She will wear him down, and then, come the kisses, along his neck, his cheeks, and her arms around him. It's then, his will starts to crack, as he begins to kiss her back, those hands of hers will untie the mask. He won't resist, he never could. So how could he tonight? But, he must! He can't keep lying to his brother.

With a sigh, he opened his eyes, the clock read one am. He had been meditating for two hours already! Standing, he started to remove his straps and belts. His hands had just finished laying his bandana neatly atop everything else, when there was a knock on the door.

Steeling himself against what he knew he must do, he breathed deep and went to the door. Opening it to reveal the petite Cassandra, her eyes were red and puffy, as if she had been crying.

"Now's not a good time Cassy." The eldest turtle forced out, trying hard not to ask her what was wrong, because then she would stay, and he didn't know how strong his will would be tonight.

Cassandra sniffed, and looked up at him, her arms wrapped around her self as if she had just felt a draft.

"Can I please, just…just talk to you?"

_Talk._ He knew better, although he wished he didn't.

"Why don't you wait for morning, and then you and Don can talk." He took a step back, preparing to shut the door.

"Because it's about Donatello!" She said, eyes growing wide with worry and fright at being shut out.

Leonardo paused, watching her carefully, her breathing was shallow with true fear, and her eyes pleaded admittance. Sighing deeply, he took two more steps back and held the door open. She moved inside the candle-lit room quietly.

Downstairs, a pair of deep brown eyes watched angrily.

"I warned ya bro…" Raphael muttered dangerously, before leaving the lair to go topside.

Inside Leo's bedroom, Cassandra took to the bed, perching on its edge nervously, while Leo sat opposite her on a chair.

"What's wrong Cassandra?" You said it had to do with Donny?"

At the sound of his name, the twenty-two year old flinched, but nodded.

"Yes, I've been thinking that I should leave, leave Donatello, and leave you, everyone. It'd be for the best, I think."

Leo's eyes widened at the thought of life without Cassandra.

"Why? Why would you want to do that Don?"

"Donatello…" She paused, and Leo noticed that he never once heard her abbreviate his brother's name. There was probably very little significance to it, but he still thought it interesting, to say the least.

"Donatello doesn't seem to care for me anymore. I'm in constant competition with his machines. And you," She gave another pained expression. Leo felt his heart trip.

"You don't really like me either, or you… I mean, have I made you mad? You've been ignoring me something awful lately."

She had her hands clasped before her tightly, and her frame began to shake as her head lowered. He watched as silent sobs wracked her tiny frame.

Without realizing what he was doing, he had moved across the room to sit beside her, as he pulled her into a hug, he brushed the tears from her face.

"Cassy, I'm not mad at you, very far from it."

Watery green eyes looked up at him.

"You're not? Then why Leo?"

_Should I tell her? No! Think of the pain it'll cause Donatello!_ He felt her hand rest on his gently and he swallowed, trying to clear his throat.

"Leo? What is it?"

Her head against his shoulder, he felt her face turn upward to him, her breath against his flesh.

"It's, nothing…"

She moved impossibly closer, and he felt his breath hitch. Her hand moved slowly up his arm. He waited, knowing that soon, her kisses would begin. Her mewling whispers and then when she turned his head to look at those pleading eyes, he won't be able to resist.

* * *

"Raph, what's this all about?" Donatello complained, hefting the sack of technological odd's and ends over his shoulder.

"Trust me bro, this is one thing ya gotta see."

He held his voice low, to hide his growing hate for his 'leader'. He knew some of the blame was Donny's. If he had just paid a little more attention to Cassy, maybe none of this would have happened.

Cassandra was a street kid that Donny had come across; she had been beat to within an inch of her life. He decided it would be safer to take her back home, and nursed her back to health. Even stayed with her through the horrible with-drawls of whatever drug she had been on.

He had spent time with her then, and she had been very grateful. The purple banded turtle had become like a hero to her. But over time, he had felt that she was okay enough to not need him every waking moment, and that he could get back to his computers. They still slept together, and he thought he was there for her, as much as he could be.

"Follow me, and be quiet!"

Thoroughly confused Donatello complied, following Raphael till they came to a stop outside Leo's bedroom door. He looked at Raph, very puzzled as the hot-tempered turtle raised a finger to his lips, and grasped the doorknob.

The door opened a few inches noiselessly, and at Raphael's insistence, Donatello peeked inside. His hazel eyes fell on the bed; there were two figures in it. He recognized Leonardo instantly, a second later, he recognized the female underneath his brother.

He felt his hands start to shake as he backed up. He looked at Raph, who gave him a sympathetic look. Don shook his head, mutters of denial on his lips. A seething rage began to wash over him, and suddenly, he heard a soft moan from inside the room.

He couldn't stand for anymore. Grabbing the door, he flung it open and stormed inside. Grabbing his brother by the edge of his shell, Donatello pulled Leo off of Cassandra and tossed him against a nearby book shelf. Cassandra screamed, pulling the covers up, hiding her naked body.

"_How could you?!" _ The purple banded turtle bellowed, still shaking with rage.

Getting to his feet, Leo raised his hands, trying to calm his furious brother.

"Don, please, I'm sorry, I never meant – "

"Oh bullshit Leo! You're sorry you got caught! I expected this from him – "He pointed a shaky finger at Raphael who looked non-plussed at the accusation.

"I _am _sorry that I hurt you…I am…" Leonardo couldn't imagine the storm of chaos inside Donatello's mind.

Donatello placed a hand over his face, trying to calm himself.

"Don?" Came Leo's hesitant voice.

"How many times?"

There was no answer.

"How many times, Leo?" He could feel the anger slithering inside him, waiting for a new opportunity to strike.

"I… I don't know. It's been a while, Don…" Leo replied, his voice riddled with pain.

"You don't know." He felt a small laugh escape as he removed his hand to open his eyes. To his right, he could see Leo's katana's.

"Don, please calm down and let's talk about this." Leo took a tentative step forward.

"Talk about what? You want to talk about all the different ways you screwed her? Is that it Leo? Find any new positions that I should know about?" He sneered, looking nothing like the soft spoken brother he had grown up with.

Leonardo looked horrified and sickened at the insinuation thrown his way.

"Donatello, Leonardo, stop this at once!" Came the strict order from their father, who stood in the doorway with Raphael and Michelangelo.

Leo turned to address Splinter, and Donatello saw his opportunity. He dove, grabbing a katana sheath, pulling out the blade. Donatello deflected the block and punch aimed at him from a surprised Leo and shoved the blade into the vulnerable flesh under the arm. The tip poking out through the other side.

"NO!" Came a joined shout from the doorway.

Donatello merely stared on grimly, revelling in the knowledge that now Leo could understand the pain he had caused him. Donatello ignored the yells from the doorway as he pulled out the katana and, thrusting it in again, he watched his brother fall, blood pooling about his feet. It was then, that he heard the crying, as the red haze of hate lifted, he watched Cassandra cradle his dying brother's head.

* * *

_fin_

_Authors Note: I don't own the turtles, I own Cassandra. The plot, and that's about it. I hope that this story is a good beginning to welcome me back into the TMNT fandom after a near three year hiatus. Please enjoy and reviews will be very appreciated, as it helps me grow to be a better writer. Also, this is a one-shot. Please don't ask for more, if I chose to write more, it is at my discretion._


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